Documents are commonly produced containing a plurality of images, and such documents often have large file sizes. As such, computer systems used to process such large documents into displayable images require a substantial amount of processing time.
Downsampling is a technique used to decrease the size of a document by reducing the number of pixels in an image. Image downsampling is used to decrease extraneous image data. Downsampling techniques include, but are not limited to, subsampling, bicubic downsampling, and average downsampling. Decreasing the size of the document allows a document to be more easily and quickly, downloaded, transmitted and/or stored.
Image downsampling can be used to optimize, for example, Portable Document Format (PDF) files. Images are often compressed in PDF files in order to increase speed and functionality. The speed and functionality is increased because a compressed image is smaller and has less bytes. Due to the decreased number of bytes, a machine may process (i.e., upload, download, save and/or print) the image at a faster speed.
For example, Acrobat® 8 from Adobe Systems, Inc. deletes an image if that image occurs multiple times within an electronic document file. Acrobat® 8 deletes a redundant image if it is fully redundant or identical in all aspects. By downsampling the image, a smaller PDF file can be created because the image is stored only a single time in the document. References to the image are used when there are multiple instances of the image in the document.